1. Field of the Invention
The invention arises from a robot system for loading equipment with general cargo units (piece goods), wherein the robot system has a gripper unit for gripping the general cargo units and a control unit for controlling the movements of the gripper unit and to determine a loading pattern of the general cargo units. The invention also concerns a method to control a robot system of the aforementioned type.
2. Description of the Prior Art
It is known to use industrial robots (in particular articulated robots) to load equipment with general cargo units, in particular to palletize (thus to load pallets with packages). Industrial robots are thereby in particular used to automate the loading of pallets with packages of different sizes with arbitrary type mix, while palletizing with homogeneous packing units (in particular with the same packing unit heights) can typically be conducted quickly and cost-effectively with automatic palletizing units). An overview of prevalent palletizing methods is provided by the monograph “Verfahren zum automatischen Palettieren von quaderformigen Packstucken in beliebigen Sortenmix” by Walter Michael Strammer, Springer-Verlag 1992. The known methods for the determination of the package positions of individual general cargo units are predominantly designed for the optimization of the degree of filling. Aspects of the stability of the loading patterns or, respectively, of the stack corresponding to the loading patterns are in all cases taken into account with low priority in a global manner when multiple selection possibilities with the same degree of filling result. The stability is then not calculated or determined, rather the loading patterns are selected so that a certain stability can be expected based on heuristic considerations.
Various heuristic algorithms for homogeneous, cuboid general cargo are described by E. E. Bischoff in: “Stability aspects of pallet loading” OR Spektrum (1991) 13: 189-197, Springer Verlag 1991. However, the heuristic algorithms are significantly limited in practice to the effect that package positions in which one general cargo unit lies on at least two other general cargo units are preferred over those package positions in which the considered general cargo unit rests on only one other general cargo unit, such that a limitations arises and towers are avoided.
In particular given very heterogeneous general cargo, the question of the stability or of the tipping moment of a loading pattern is very complex, and a persistent calculation is not possible since no complete description of the objects exists. Elasticity, damage, precise position of the center of gravity and other things are normally unknown. Error tolerances add to this. The size of the packages is only known to approximately 0.5 cm in each direction. A determination can therefore in particular not be conducted in real time by control computers of known robot systems, thus not in a time period that is small in comparison to typical or desired load times. Therefore the question of the stability of a loading pattern or, respectively, of a package stack generated by the robot system remains open, such that a complicated wrapping (for example made of film) is necessary in any case for transport.